As organic compounds being added to cement, a naphthalenesulfonate-formaldehyde condensate, a melamine-sulfonate-formaldehyde condensate, a ligninsulfonate, etc., are used as a water reducing agent and also polyethylene glycol methyl ether, polyoxyethylenepolyoxypropylene glycol, etc., are used as a dry shrinkage preventing agent.
These additive are used in the case of kneading a composition composed of cement, water, etc. However, although these additives may have an effect of reducing the amount of water at use or an effect of preventing the occurrence of dry shrinkage after operation, the use of these additives cannot avoid the reduction with time in fluidity of the cement composition (so-called slump-loss).
Japanese Patent Application (OPI) No. 162162/84 (the term "OPI" as used herein indicates an "unexamined published application") discloses that the use of a naphthalenesulfonate-formaldehyde condensate or a melaminesulfonate-formaldehyde condensate together with a copolymer of an allyl alcohol (alkylene oxide addition product) and an unsaturated dicarboxylic acid (alkylene oxide addition product) is effective for the improvement of the slump-loss but the effect is not always sufficient.
The slump-loss is the most serious problem in the field of cement industry. If the problem is solved, not only the loss at the application of concrete is reduced but also the usable life or period of concrete is greatly prolonged. Thus, early solving of the problem has been desired.